It is known in the art that a cam system, which may include, for example, a cam shaft and rocker arm, can be employed to open and close a valve of an internal combustion (IC) engine. An example of a standard cam profile engine valve opening/closing curve 300a is generally shown in FIG. 3.
The timing of engine valve closure during an IC engine's induction stroke may be varied to, among other things, optimize the performance of the engine. Variable valve timing in the closing of the engine valve can be accomplished by, for example, employing a hydraulic force actuator that counteracts the closing force of the valve spring. As generally illustrated in FIG. 3, the delayed closing movement of the engine valve (generally represented in the Figure by 301) is often referred to as an “added motion.”
Although current added motion systems can provide a desired delayed closing movement of a valve, temperature and viscosity variations of an associated fluid, such as, for example, engine oil, may result in an inconsistency in the timing of the closing of the engine valve. FIG. 3 generally illustrates a seating variation (shown generally by segment 403).
Accordingly, a need exists to provide an added motion system that can provide controlled engine valve seating and controlled added motion closing movement to a valve over a wide range of fluid temperatures and/or viscosities.